Bi-Directional Bus Repeater

1. A bi-directional bus repeater comprising one or more repeater units, each repeater unit comprising: a first input terminal; a second input terminal; a first pulldown element for pulling down a voltage at the first terminal in response to a first control signal; a second pulldown element for pulling down a voltage at the second terminal in response to a second control signal; a first pulldown controller for providing the first control signal in dependence of a voltage at the second input terminal; a second pulldown controller for providing the second control signal in dependence of a voltage at the first input terminal; wherein the first pulldown controller comprises a first input connected to the first input terminal using a first connection and a second input connected to the second input terminal using a second connection; wherein the first pulldown controller is configured to provide the first control signal for activating the first pulldown element only after simultaneously detecting a high-to-low transition at its second input and a logical high at its first input; wherein the second pulldown controller comprises a first input connected to the second input terminal using a first connection and a second input connected to the first input terminal using a second connection; and wherein the second pulldown controller is configured to provide the second control signal for activating the second pulldown element only after simultaneously detecting a high-to-low transition at its second input and a logical high at its first input.

2. The bi-directional bus repeater according to claim 1, further comprising a time delay existing between a voltage at the first input of the first pulldown controller and a voltage at the second input of the second pulldown controller so that the second pulldown controller is prevented from providing the second control signal for activating the second pulldown element when the first pulldown element is active; and a time delay existing between a voltage at the first input of the second pulldown controller and a voltage at the second input of the first pulldown controller so that the first pulldown controller is prevented from providing the first control signal for activating the first pulldown element when the second pulldown element is active.

3. The bi-directional bus repeater according to claim 1, wherein the bi-directional bus repeater is configured to be placed in an open-drain communication bus that is configured for implementing the Inter-Integrated Circuit, I2C, protocol.

4. The bi-directional bus repeater according to claim 1, wherein the first pulldown element and the second pulldown element each comprise a transistor; and/or wherein the bi-directional bus repeater comprises a plurality of the repeater units, wherein the plurality of repeater units is integrated on a same semiconductor die and/or housed in a same package.

5. The bi-directional bus repeater according to claim 1, wherein the first pulldown controller comprises a third input connected to the second input terminal through a third connection, the first pulldown controller being configured for deactivating the first pulldown element when detecting a logical high at its third input; and wherein the second pulldown controller comprises a third input connected to the first input terminal through a third connection, the second pulldown controller being configured for deactivating the second pulldown element when detecting a logical high at its third input.

6. The bi-directional bus repeater according to claim 1, wherein the first pulldown controller comprises a first flip-flop and the second pulldown controller comprises a second flip-flop; and wherein the first flip-flop and the second flip-flop each comprise a negative edge triggered D flip-flop, the flip-flop having a data input corresponding to the first input, a clock input corresponding to the second input, a reset input corresponding to the third input, and a state output connected to the first pulldown element or the second pulldown element, respectively.

7. The bi-directional bus repeater according to claim 2, wherein the first connection connecting the first input terminal to the first input of the first pulldown controller and the second connection connecting the first input terminal to the second input of the second pulldown controller comprise a shared part extending between the first input terminal and a first node; wherein the first connection connecting the second input terminal to the first input of the second pulldown controller and the second connection connecting the second input terminal to the second input of the first pulldown controller comprise a shared part extending between the second input terminal and a second node; and a time delay between the first node and the second input of the second pulldown controller is much larger than a fall-time associated with a high-to-low transition of a voltage at the second node occurring as a result of a high-to-low transition occurring at the second input terminal, and a time delay between the second node and the second input of the first pulldown controller is much larger than a fall-time associated with a high-to-low transition of a voltage at the first node occurring as a result of a high-to-low transition occurring at the first input terminal.

8. The bi-directional bus repeater according to claim 4, wherein the transistor is a field-effect transistor.

9. The bi-directional bus repeater according to claim 4, wherein the transistor is an n-channel metal-oxide-semiconductor field-effect transistor.

10. The bi-directional bus repeater according to claim 5, wherein the first pulldown controller is configured to perform the deactivating in response to detecting a logical high at its third input regardless the inputs received at its first input and its second input; wherein the second pulldown controller is configured to perform the deactivating in response to detecting a logical high at its third input regardless the inputs received at its first input and its second input; wherein the third connection between the second input terminal and the third input of the first pulldown controller and the second connection between the second input terminal and the second input of the first pulldown controller comprise a shared part extending between a third node and the second input terminal; a time delay between the third node and the second input of the first pulldown controller is such that a high level at the third node will deactivate the first pulldown element regardless the input at the second input or first input thereof; wherein the third connection between the first input terminal and the third input of the second pulldown controller and the second connection between the first input terminal and the second input of the second pulldown controller comprise a shared part extending between a fourth node and the first input terminal; and a time delay between the fourth node and the second input of the second pulldown controller is such that a high level at the fourth node will deactivate the second pulldown element regardless the input at the second input or first input thereof.

11. The bi-directional bus repeater according to claim 5, wherein the second connection between the first input terminal and the second input of the second pulldown controller comprises a first level shifter, and wherein the second connection between the second input terminal and the second input of the first pulldown controller comprises a second level shifter.

12. The bi-directional bus repeater according to claim 7, wherein the first connection between the first input terminal and the first input of the first pulldown controller comprises a first Schmitt trigger having a buffered output; wherein the first connection between the second input terminal and the first input of the second pulldown controller comprises a second Schmitt trigger having a buffered output; wherein the first Schmitt trigger having a buffered output comprises a first series connection of a first Schmitt trigger and a first buffer; an input of the first series connection is connected to the first input terminal and an output of the first series connection to the first input of the first pulldown controller and to the second input of the second pulldown controller; wherein, the first Schmitt trigger is an inverting Schmitt trigger and the first buffer is an inverter; wherein the second Schmitt trigger having a buffered output comprises a second series connection of a second Schmitt trigger and a second buffer; an input of the second series connection is connected to the second input terminal and an output of the second series connection to the first input of the second pulldown controller and to the second input of the first pulldown controller; wherein the second Schmitt trigger is an inverting Schmitt trigger and the second buffer is an inverter; and wherein the first Schmitt trigger having a buffered output is arranged in between the first node and the first input terminal, and the second Schmitt trigger having a buffered output is arranged in between the second node and the second input terminal.

13. The bi-directional bus repeater according to claim 11, wherein the first level shifter comprises: an input connected to the first input terminal, or to the output of the first series connection; and an output connected to the second input of the second pulldown controller and to the third input of the second pulldown controller; wherein the first level shifter further comprises a first supply voltage terminal for receiving a first supply voltage and a second supply voltage terminal for receiving a second supply voltage different from the first supply voltage; wherein the first pulldown controller and the first Schmitt trigger and the first buffer are fed using the first supply voltage; and wherein the first level shifter is configured to translate a voltage range of a voltage received at its input referenced to the first supply voltage to a voltage range of a voltage outputted at its output referenced to the second supply voltage.

14. The bi-directional bus repeater according to claim 11, wherein the second level shifter comprises: an input connected to the second input terminal, or via the output of the second series connection; and an output connected to the second input of the first pulldown controller, and to the third input of the first pulldown controller; wherein the second level shifter further comprises a first supply voltage terminal for receiving a first supply voltage and a second supply voltage terminal for receiving a second supply voltage different from the first supply voltage; wherein the second pulldown controller and the second Schmitt trigger and the second buffer are fed using the second supply voltage; and wherein the second level shifter is configured to translate a voltage range of a voltage received at its input referenced to the second supply voltage to a voltage range of a voltage outputted at its output referenced to the first supply voltage.

15. The bi-directional bus repeater according to claim 13, each repeater unit further comprising: a first delay element having a buffered output arranged between the output of the second level shifter and the second input of the first pulldown controller, wherein the first delay element is fed using the first supply voltage; and a second delay element having a buffered output arranged between the output of the first level shifter and the second input of the second pulldown controller, wherein the second delay element is fed using the second supply voltage.

16. The bi-directional bus repeater according to claim 14, each repeater unit further comprising: a first delay element having a buffered output arranged between the output of the second level shifter and the second input of the first pulldown controller, wherein the first delay element is fed using the first supply voltage; and a second delay element having a buffered output arranged between the output of the first level shifter and the second input of the second pulldown controller, wherein the second delay element is fed using the second supply voltage.

17. A bi-directional communication bus, comprising: a first segment comprising one or more bus lines; a second segment comprising one or more bus lines; wherein each bus line of the first segment forms a pair with a respective bus line of the second segment; a bus repeater as defined in claim 1 comprising a respective repeater unit for each pair of bus lines; wherein the first input terminal of a given repeater unit is connected to a given bus line of the first segment; wherein the second input terminal of that repeater unit is connected to the bus line of the second segment that forms a pair with the given bus line of the first segment; wherein the bi-directional communication bus further comprises, for each bus line of the first and second segments, a pullup element; wherein the pullup element is a resistor connected in between a respective bus line and a supply voltage; and wherein the bi-directional communication bus is an open-drain communication bus that is configured for implementing the Inter-Integrated Circuit, I2C, protocol.

18. A communication system, comprising a: a first communication unit; a second communication unit; the bi-directional communication bus as defined in claim 17 for connecting the first communication unit and the second communication unit; and wherein each of the first communication unit and second communication unit is configured to transmit data to the other communication unit by pulling down a voltage at a bus line of the first segment or second segment of the bi-directional communication bus it is connected to.